Hi,
Apologies for the delay of the response.
Unfortunately, AD5933 won't be able to measure as low as 0.1Ω.
As said in the datasheet, 100Ω to 1KΩ can be measured by adding external circuitry.
What we have tried is changing the excitation voltage to 1Vpp and we were able to measure 40Ω. The downside of this, is the range of the measured impedance will also change -- that is, the range becomes smaller.
you might want to explore aducm350. I saw an FAQ by Liam Riordan: ADuCM350 FAQ DFT / Impedance Measurement
It says it can measure subohm to Mohms. But you may want to ask them more about it: ADuCM350
Hope this helps.
-Sittie